Dark skies preservation

For many people great joy comes from simply standing beneath a clear dark sky and marvelling at the heavens. Today, however, an increasing majority of people can no longer see the true beauty of the night sky from their homes. Even some of the brightest stars are lost in the glare of light pollution. The sight of the Milky Way stretching across the night sky is for many of us a childhood memory; sadly, today a generation is growing up having never seen our own galaxy, the place we call home in the Universe. Light from the rest of the Universe can take billions of years to reach our eyes — it seems such a pity to lose it in the last millisecond of its journey!

Astronomers define light pollution as “artificial light that shines where it is neither wanted, nor needed”. The most obvious everyday manifestation of light pollution is in the increasing illumination of our night sky and the subsequent difficulties in observing astronomical objects from polluted locations. Light from poorly designed, incorrectly directed light fixtures shines into the sky. There, it is scattered by air molecules, moisture and aerosols in the atmosphere causing the night sky to light up; a phenomenon known as sky-glow.

Light pollution does not only affect astronomers. Anyone could be disturbed by the intrusion of light, be it a street lamp that shines into a bedroom or the glare of a poorly designed street light that dazzles a motorist. Light pollution also has numerous direct impacts on the environment; it puts a great strain on wildlife in both urban and rural locations who become disoriented by bright lights (read more). It is an unnecessary waste of energy that results in great cost to economies worldwide (read more), for example some high-powered lights produce more carbon dioxide over a year than a modern day diesel car produces by travelling about 500 kilometres. The 2017 Nobel Prize in Physiology or Medicine was given to a group whose discoveries suggest that the human body clock requires natural daylight rhythms and dark skies in order to function properly (read more).

Light pollution and other electromagnetic interference affect amateur astronomers and professionals and their observatories alike. Today, the European Southern Observatory works to protect existing and potential observatory sites from pollution at all wavelengths of the electromagnetic spectrum, preserving important dark sky sites around the world.

ESO understands that dark skies are important around the world, not only in Chile. ESO has supported the organisation of an initiative presented by the International Astronomical Union (IAU) at the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) to organise an international conference on the harmful effects of light pollution for astronomy, and also for ecosystems and for human health.